The term "trust fund" can simply be defined as a collection or pool of property, mostly in the form of securities or money. These pools of funds are usually held by a party, such as a parent or a guardian, for the benefit of some other party such as a child.
A trust fund can also be explained as the corpus (the principal) of any trust. The principal or the corpus of a trust fund usually consists of its assets, which may sometimes also include any accumulated profits made from the assets of the fund.